What Is an Accessory Dwelling Unit (ADU)?
An accessory dwelling unit (ADU) is a secondary dwelling built on the same lot as a primary residence. These units go by several names — granny flat, in-law suite, backyard cottage, or Casita — and have grown in popularity as a practical way to add living space or generate rental income without purchasing a separate property.
ADUs can serve a range of purposes: housing for extended family members, a rental unit, a home office, or a guest house. Their flexibility makes them an appealing option for homeowners looking to make better use of their existing property.
ADU Types Offered by Brothers General Construction Company
Brothers General Construction Company works with homeowners across Illinois to build a variety of ADU types, tailored to each client's specific situation and property. The types they offer include:
- Detached ADUs — Standalone structures such as tiny homes and backyard cottages, usable as rental units, guest houses, or living spaces for family members.
- Attached ADUs — Additions or conversions within the existing footprint of the home, including basement and attic conversions.
- Junior ADUs (JADUs) — Internal units carved out of existing space within the primary residence, offering a more compact and cost-effective solution.
- Garage conversion ADUs — Transforming an existing garage into a functional living space, a practical option for properties where a detached build may not be feasible.
For each project, Brothers General Construction Company works to ensure that all applicable safety and zoning requirements are met, helping clients navigate the regulatory process from start to finish.
In Chicago, the ADU Ordinance passed in May 2021 allows for the construction of accessory dwelling units in most residential areas of the city. The ordinance covers detached, attached, internal, and garage conversion ADUs, and is intended to help address the city's housing shortage while giving property owners the opportunity to earn additional income through rentals.
Costs and Rental Income Potential
The cost of building an ADU in Chicago can vary depending on the size, complexity, materials, and contractor involved. On average, homeowners can expect to spend between $115,000 and $150,000 for an ADU build in Chicago. This estimate does not include design and permitting fees, or city plumbing and electrical costs, which should be factored into the overall budget.
One reason many homeowners pursue ADU construction is the potential for rental income. For those considering short-term rentals through platforms like Airbnb or VRBO, an ADU can offer meaningful returns. As a general illustration, an ADU rented at $250 per night with a 90% occupancy rate could generate approximately $6,750 per month — though actual earnings will depend on location, unit size, amenities, and local demand.
It's also worth accounting for ongoing costs such as cleaning, utilities, and general maintenance when evaluating the financial picture of a short-term rental ADU.
Brothers General Construction Company serves homeowners throughout Illinois, from Chicago to more rural parts of the state. As an experienced ADU builder and garage conversion contractor, they handle projects from initial design through final construction, working alongside clients to develop units that fit their needs while complying with local building codes and zoning regulations.
